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PC Historian Finds Puzzling Game Diskette Image
This past weekend, Trixter — a self-proclaimed IBM PC historian — picked up some old software for his archive. What he didn't count on was a couple of additional Avantage titles that had never been released into the wild. If this weren't enough of a find, one of these titles provided Trixter with an interesting puzzle: the diskette for Mental Blocks is apparently hand-formatted to work on both C64 and IBM (on a single side, not the "flippy disks" of old). Quite an interesting little piece of history.
*looks at his hybrid Blizzard game disks and smiles* It goes to show that these days, everything new is an old idea!
With a tiny magnet, flipping 1's and 0's.
Wonder how many patents this potentially invalidates?
(wow...my first slashdot post in like 5+ years...something I actually can know stuff about! LOL)
I wanted to email Trixter this but couldn't find a contact email.
It's been now about 25 years but I still have parts of the C64 ROM's memorized. There was a time that I knew pretty much what every byte in the 64k(*) of memory was for cold without needing a reference manual. Having said that:
This wouldn't have been all that hard to do by somebody who had intimiate knowledge of *both* IBM and C64 formats I'd imagine. First, I doubt it was done 'by hand' as in a manual sector by sector copy. A program would have been written, using a slave-master 2 drive config, to stream from the source drive to the dest. drive using a list ot sectors/tracks and/or using a simple formula to calc where the tracks should go. You simply would pick areas on the C64 side that you would want reserved for the IBM side and vica versa. Knowing both IBM and C64 MFM structures would allow you to pick "safe" areas for both formats.
Oh, and the directory structure of the C64 did indeed live on track 18. All the other data blocks where chained out as a linked list from the entry in this track.
All that would have been really needed is:
#1) Format the disk for IBM and use whatever areas you need via a streamed block by block copy from Src to Dst.
#2) Noting which tracks are "safe" to use on the C64, simply write a program to format track by track and write the C64 data, streaming again.
Ingenious, but really not that hard at all...
(*) Well, more like ~80k with the shadow RAM near the top of the 64k range...
Ted
This does look like a very early example, but the technique is not as novel and amazing as the article makes out.
For example, in the UK around 1989 there was a magazine for Atari ST and Amiga users called "ST/Amiga Format" that used a hybrid format on 3.5" coverdisks. The ST used a PC-like 720MB format, whereas the Amiga had its own filesystem that fitted 880MB on the same disk. The hybrid disks weren't flippable, they were read double-sided on both systems and just marked the part of the disk used for the other filesystem as bad.
The short-lived, dual-format ST/Amiga Format magazine from the late 1980s also had an appropriately dual-format cover-disk - somehow combining the apparently wildly-incompatible ST and Amiga floppy disk formats.
I've no idea how it was done (although the fact that many STs had single-sided floppy drives may have had something to do with it) - and while it could have been extremely useful to publish games in such a manner at the time, I don't know that was ever done either.
I get the impression that there was a lot of deep magic involved in these enhanced disk formats, copy protection systems and so on. I'm sure the name Rob Northen appeared on the front of a later ST Format cover disk - as the supplier of the fancy files-limited-to-particular-sides-of-disk format used to not deprive single-sided drive owners the contents of the entire double-sided disk...
Tedious Bloggy Stuff - hooray?
It's just another case of corruption on an 8088 ;-)
(If you know Trixter, then you know what I'm talking about ... http://www.oldskool.org/pc/8088_Corruption )
For some reason it reminds me of the floppy records that came inside magazines, when I was a kid. We would transfer the audio from the record to a cassette, then load the cassette into the computer.
Nobody even whispered, because we were convinced the least bit of sound would get mixed in and corrupted the whole thing. Same goes for acoustic-couple modems, except it really worked that way sometimes. Too much background noise and you'd lose carrier.
Ahhh.. the good old days.
Never ask for directions from a two-headed tourist! -Big Bird
This is a cool hack. From what it looks like, this is possible because DOS put the boot sector and the root directory in the beginning of the disk, whereas the C64 made the sane choice of putting it in the middle (think about it, this minimizes seek times). Now the directory (or, more precisely, the File Allocation Table (=FAT)) contains information on so-called bad blocks, i.e. blocks that the OS shouldn't write to because they were known to be bad. If you label the blocks that you put the C64 data into as bad blocks, then DOS is not going to overwrite the C64 data. Now you do the same in the C64 FS and bang -- double OS format created. And it's read/write!
I wonder if someone managed to format a disk such that one was also able to share the data space between the different OSs?
This one is relatively easy to do, since DOS uses track 0 to find the directory, and the C64 keeps the directory on a middle track. Even better, the whole second side of the disk could be formatted for PC sectors. But you do have to put the disk through two duplicators, one for the PC sectors, and another for the C64 sectors. (Nowadays this could be done with a Catweasel or similar disk controller that deals with times between transitions.)
This is pretty impressive, but it only needs one format per track. There have been cases where the same track was in multiple formats. The TRS-80 Model I booted from a single-density T0S0, while the Model III booted from a double-density T0S0. There were autoboot games which formatted sectors on track 0 in both single and double density.
As I heard it, the first part of the trick is that the Model I switched density by having both types of disk controller chips. (I don't know details of how the III did it) The second part of the trick is that you start one of the FDC chips formatting a track, then interrupt it partway through. Then you start the other FDC formatting the rest of the track. Presto, you have a track with sectors in both densities! You don't need any other data on track zero, as the boot sectors were customized to boot from the rest of the disk in single density, which both a M3 and an standard single-density M1 could read.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
Not only that, but on a 3.5" floppy too!
LOL, ok that KB, not MB.
If memory serves me right, the disks you're thinking of were from Mastertronic or possibly Epyx (specifically, World Championship Karate, the only game by Epyx I had on floppy). There's a chance that it could have been one of Datasoft's games as well.
Fifty watts per channel, baby cakes.
Pfft. Real programmers just think really hard, choosing the proper universe such that electrons happen to tunnel at just the right place and time to affect the magnetizer.
Even better ones choose the universe in which the atoms of the proper hard disk spontaneously tunnel into just the right configuration from across spacetime.
Can you be Even More Awesome?!
That was the first game that I pirated... after I bought it.
The copy protection was so messed up that the only way I could get a copy of the game that was reliable was a cracked copy. But I didn't want a pirated diskette, so I had the cracked copy written over the original gold-labelled floppy.
I clicked on the story thinking he had found some kind of strange Goatse image embedded in the disk. I was very disappointed.
Thank you for that. I'll never be able to look at the spindle hole of an 8" or 5.25" disk the same way again.
Oh, say does that Star-Spangled Banner entwine / The myrtle of Venus with Bacchus's vine?
This game used a custom hybrid format so the same game disk worked on both ATARI ST and AMIGA.
http://en.wikipedia.org/wiki/Starglider_2
This is a somewhat common attack vector for Windows. A malware author creates a data/audio CD and then distributes it as an audio CD. If the victim puts it in their CD player, it plays fine*. If they put it into their Linux machine, and then play it like an audio CD it plays fine. But when they put it into their Windows machine, Windows (by default) recognizes the CD as data, and then loads the autorun program, which is a trojan horse.
Sony's rootkit a few years ago did exactly this.
* Some people here are saying that a CD player will attempt to play the data track as audio, and it will be random noise. I have never experienced this from data/audio CDs.
Write your own Choose Your Own Adventure. http://www.freegameengines.org/gamebook-engine/
Seriously. If somebody did this today, it would be featured on the daily wtf.
After all, I am strangely colored.
When I had my Amiga 1000 we had software that could do an Amiga, Macintosh, and MS-DOS format on the same floppy disk. You took like 100K to 200K parts of the disk and made a mini-format for each standard.
There used to be software that made mini-standards and it was affordable for game companies to use the same floppy disk with two or more versions of their game on two different partitions of a floppy disk.
For example one was a MFM format for the PC and the other was a GCR format for the C64.
That was old school hacking, before "War Games" and people trying to crack computers and security and writing viruses. It is more of a computer hobbyist style of tweaking a computer that we computer geeks liked to use back in those days when being a "hacker" meant you wrote useful code that nobody else could to do impossible things like one floppy disk that supports two different formats at the same time. Back in the old days when programmers used machine code and assembly language and BASIC interpreters with peek and poke statements. Long before the GUI revolution and long before script-kiddies called themselves the new hackers, and are really crackers and not hackers at all.
Remember, Slashdot does not have a -1 disagree moderation, and no, troll, flamebait, and overrated are not substitutes.
Starglider (from Rainbird) for Amiga & ST did this too. It really amazed me at the time especially because one side of the disk contained a sampled song that played at startup, so the exactly the same data was being played on both the rubbishy ST Yamaha sound chip and the awesome Amiga chip...Paula was it? I can't remember.